<template>
  <div class="container">
    <!-- 固定导航 -->
    <van-nav-bar fixed left-arrow @click-left="$router.back()" title="小思同学">
    </van-nav-bar>

    <!-- 聊天主体区域 -->
    <div class="chat-list">
      <div v-for="(obj, index) in list" :key="index">
        <!-- 左侧是机器人小思 -->
        <div class="chat-item left" v-if="obj.name !== 'me'">
          <van-image
            fit="cover"
            round
            src="https://img.yzcdn.cn/vant/cat.jpeg"
          />
          <div class="chat-pao">{{ obj.msg }}</div>
        </div>
        <!-- 右侧是当前用户 -->
        <div class="chat-item right" v-else>
          <div class="chat-pao">{{ obj.msg }}</div>
          <van-image
            fit="cover"
            round
            :src="$store.state.userPhoto"/>
        </div>
      </div>
    </div>

    <!-- 对话区域 -->
    <div class="reply-container van-hairline--top">
      <van-field placeholder="说点什么..." v-model="word">
        <template #button>
          <span style="font-size: 12px; color: #999" @click="sendFn">提交</span>
        </template>
      </van-field>
    </div>
  </div>
</template>

<script>
import { io } from 'socket.io-client'
import { getToken } from '@/utils/token'
export default {
  data () {
    return {
      word: '', // 输入框的内容
      list: [ // 所有聊天内容
        { name: 'xs', msg: 'XXXX' },
        { name: 'me', msg: 'hi' }
      ],
      socket: null// 客户端和服务器建立链接的socket对象
    }
  },
  created () {
    // 注意：io是建立socket链接，和axios没有任何关系
    this.socket = io('ws://geek.itheima.net',
      {
        query: { token: getToken() },
        transports: ['websocket']
      })
    // 测试下是否建立链接成功
    // this.socket.on('connect', () => { console.log('建立连接成功') })

    // 接收后端传回来的信息
    this.socket.on('message', obj => {
      this.list.push({ name: 'xs', msg: obj.msg })
      // 滚动到最下面
      this.scrolL()
    })
  },
  methods: {
    // 滚动屏幕
    scrolL () {
      this.$nextTick(() => {
        const theDiv = document.querySelector('.chat-list>div:last-child')
        theDiv.scrollIntoView({ behavior: 'smooth' })
      })
    },
    // 发送信息
    sendFn () {
      // 用socket对象.emit('后端接收信息的事件名',值)
      this.socket.emit('message',
        {
          msg: this.word,
          timestamp: new Date().getTime()
        })
      this.list.push({ name: 'me', msg: this.word })// 消息显示到页面上
      this.word = ''// 清空输入框
      // 滚动到最下面
      this.scrolL()
    }
  },
  destroyed () { // 销毁阶段【关闭socket服务】
    this.socket.close()
    this.socket = null
  }
}
</script>

 <style lang="less" scoped>
.container {
  height: 100%;
  width: 100%;
  position: absolute;
  left: 0;
  top: 0;
  box-sizing: border-box;
  background: #fafafa;
  padding: 46px 0 50px 0;
  .chat-list {
    height: 100%;
    overflow-y: scroll;
    .chat-item {
      padding: 10px;
      .van-image {
        vertical-align: top;
        width: 40px;
        height: 40px;
      }
      .chat-pao {
        vertical-align: top;
        display: inline-block;
        min-width: 40px;
        max-width: 70%;
        min-height: 40px;
        line-height: 38px;
        border: 0.5px solid #c2d9ea;
        border-radius: 4px;
        position: relative;
        padding: 0 10px;
        background-color: #e0effb;
        word-break: break-all;
        font-size: 14px;
        color: #333;
        &::before {
          content: "";
          width: 10px;
          height: 10px;
          position: absolute;
          top: 12px;
          border-top: 0.5px solid #c2d9ea;
          border-right: 0.5px solid #c2d9ea;
          background: #e0effb;
        }
      }
    }
  }
}
.chat-item.right {
  text-align: right;
  .chat-pao {
    margin-left: 0;
    margin-right: 15px;
    &::before {
      right: -6px;
      transform: rotate(45deg);
    }
  }
}
.chat-item.left {
  text-align: left;
  .chat-pao {
    margin-left: 15px;
    margin-right: 0;
    &::before {
      left: -5px;
      transform: rotate(-135deg);
    }
  }
}
.reply-container {
  position: fixed;
  left: 0;
  bottom: 0;
  height: 44px;
  width: 100%;
  background: #f5f5f5;
  z-index: 9999;
}
</style>
